1. Field of the Invention
This invention relates to a process for preparing azo coloring materials, i.e., dyes and pigments. More specifically, this invention relates to an improved process for preparing azo dyes and pigments characterized by improved consistency and reproducibility of the dyes and pigments produced thereby.
2. Description of the Prior Art
Azo coloring materials have traditionally been prepared on a commercial scale by a multi-step procedure. That procedure involves preparing an appropriate aqueous solution or dispersion of a diazonium salt of a primary amino compound in one reaction vessel, preparing an appropriate aqueous solution or dispersion of a coupling compound in a second vessel and either adding one of these masses to the other or mixing them in a third vessel. It is well known in the prior art to employ phenols, naphthols, etc., and particularly beta-naphthols and beta-naphthol substituted compounds as couplers in the production of azo dyes and pigments. However, production of azo dyes and pigments by the conventional prior art processes often results in batch to batch inconsistencies and lack of reproducibility of the azo dye or pigment produced.
It is a purpose of the instant invention to provide a process for producing azo dyes and pigments, by coupling with beta-naphthols and beta-naphthol substituted compounds, characterized by improved consistency and reproducibility of the product.
______________________________________ Pertinent Prior Art References Patent No. Issued Inventor Assignee ______________________________________ 4,046,754 9/6/77 Meininger et al Hoechst 3,793,305 2/19/74 Balon DuPont 4,014,866 3/29/77 Henning BASF ______________________________________